SIGMAR1 gene-related neuromuscular disorders - what do we know?

Distal hereditary motor neuropathies (dHMNs) are a clinically and genetically diverse group of rare neuromuscular disorders characterized by progressive distal muscle weakness and atrophy, often with early onset and sparing of sensory function. One subtype, Jerash-type dHMN (dHMNJ), is caused by biallelic mutations in the SIGMAR1 gene and presents with pyramidal signs in addition to distal weakness.

A literature review was conducted by searches of the MEDLINE and PubMed databases using selected terms. Relevant original articles, case reports, case series, and reviews were selected as data sources.

SIGMAR1-related disorders (SIGMAR1-RD) encompass a broad clinical spectrum including dHMN and juvenile amyotrophic lateral sclerosis (ALS) phenotypes. The Sigma-1 receptor plays a key role in cellular stress responses, ER-mitochondria interaction, and neuronal survival. Clinical presentation often includes distal muscle weakness and atrophy with pyramidal signs.

We present a 12-year-old boy with distal muscle weakness, foot drop, and pyramidal signs. Genetic testing identified a homozygous c.247T > C (p.Phe83Leu) SIGMAR1 variant, previously classified as a variant of uncertain significance (VUS).

This article supports the pathogenicity of the c.247T > C (p.Phe83Leu) SIGMAR1 variant and underlines the need for broader genetic testing in hereditary motor neuropathies.